When you say good portions. Like 5 small meals a day spaced 3 hours apart? What supplements should I have her take? I was thinking a multi-vitamin and get her a protein powder so she can have that in the morning and after workouts.
I said keep it simple.
Don't try to change what, or how often, she eats. She ask her to say no to crap food (chips, ice cream, candy, etc.)
one out of three times.
As for what constitutes a "portion", tell he to limit what ever she's eating to a cup (the measurement) or so. Dinner might be a 6 oz of steak, a baked potato (whatever topping she wants), and a small salad.
Again, you're not trying to get her to eat
healthy yet, you're just trying to get her to eat
responsibly.
If you decided to take up running, would you start by trying to do a 10k marathon? Of course not! The problem is that, when people try to clean up their diet, they try to run a marathon of perfect foods, perfect portions, perfect meal timing, and supplements. This is going to lead to failure.
If you help her to take it slowly, you'll help her to succeed.
Another thing that's easy to do, is to get her to switch to diet if she's a soda drinker. That, along with the other two things, will significantly cut down on her caloric intake without making her feel like she's on a diet and triggering any negative feelings about changing her diet.